Infrared coatings – case studies 2020

May 11, 2020

Infrared coatings

0.75 – 20 µm

Overview, capabilities, case studies


Infrared coatings on crystals, windows, or optical substrates at 3photon coating facility are deposited every day to produce high quality infrared optical components. IR coated components are used in spectroscopy, medical, military, astronomy applications, in such devices as lasers, thermal imaging gadgets, detectors, etc. There are three main ranges in terms of wavelength:

  • SWIR/NIR (Short wave/Near infrared): 750 nm – 3000 nm (0.75 – 3.0 µm)
  • MIR/MWIR (Medium/Mid-/Middle wave Infrared): 3.0 – 5.0 µm
  • LWIR/FIR (Long wave infrared/ Far infrared): 5.0 – 8.0 – 14.0 – 20.0 µm

Infrared coatings


3photon experienced team of quality assurance professionals can handle sensitive materials and our coating engineers and physicists can design and apply several types of infrared coatings:



Case studies – AR coatings on infrared (IR) crystals

TASK: Develop High LIDT coatings to increase efficiency of absorption and transmission bands of ZGP crystal

ZGP crystal (Zinc Germanium Phosphide) is widely used in infrared range, usually in imaging or defense applications. Very precise procedure is required to avoid contamination and produce ZGP crystals with maximal laser damage threshold. 3photon team designed and applied coatings where LIDT >2 J/cm2 @ 2.1 µm, 20 ns, 10 Hz, was not a limit.



TASK: Design complex AR coating solution on AgGaSe2 crystal for SWIR and FWIR

AGSe (AgGaSe2 or silver selenogallate) is widely used IR crystal and champion in three-wave interactions. It is used as an alternative to ZGP crystal, in infrared optical parametric oscillators (IR OPO), and harmonic generation. Our coating on AGSe crystal was designed to increase crystal’s overal performance.



Case studies – Coatings on infrared (IR) waveplates

TASK: Reduce reflection of infrared crystal surfaces in IR waveplate @ 7.0 – 9.5 μm

Infrared waveplates can be coated with anti-reflection coating to increase transmission by reducing light losses. 3photon engineers designed and deposited durable infrared coating on middle wave infrared waveplate made of infrared crystal.



TASK: Increase transmission of MgF2 IR waveplate @ 5.8-6.0 μm

Infrared waveplates made from MgF2 can also be easily AR coated to increase performance. Coating can be optimized for specific wavelength or broad range of infrared wavelengths.


Case studies – Infrared coatings on calcium fluoride

TASK: Produce broadband (BBHR) MWIR mirror for medical laser

This specific broad band infrared mirror coating is designed for low power applications. Coating was deposited with electron beam evaporation method. Due to porosity of the coating waterline can be observed around 2900 nm region, yet still, high reflection values at 2.9 μm can be achieved. To avoid waterlines, more dense coatings (e.g. Ion beam sputtering) should be used.



TASK: Filter out 1064 nm from MWIR

When very far infrared is not necessary – Calcium fluoride can be used as substrate for dichroic mirror. Our engineers designed and applied IR coating to filter out 1064 nm from middle wave infrared.



Case studies – Broadband AR coatings on Silicon (Si) and Germanium (Ge)

TASK: Increase transmission of Silicon (Si)  and Germanium (Ge) in MWIR (3000-5000 nm)

Wide-band AR coating 3000-5000 nm (3-5 μm) can be applied on Silica or Germanium windows to increase performance – decrease reflection per surface and maximizing overall transmission throughout whole element.

Anti-reflection coating on Silicon (Si) can be designed as per bellow curve:

A little bit better performance can be observed of anti-reflection coating on Germanium (Ge):


Case studies – IR coating on undoped and doped ZnSe and ZnS

TASK: Filter out 1310 nm or 785 nm from MWIR and FWIR

To filter out infrared spectra from specific wavelength, 3photon suggests infrared dichroic mirror coatings on zinc selenide (ZnSe) substrates.



TASK: Design universal dichroic coating on Fe:ZnSe and Fe:ZnS q-switch crystals to substitute IR optical components in laser cavity

3photon developed special coating design, which increases pumping efficiency. Furthermore, this coating can be applied on both Fe:ZnSe and Fe:ZnS crystals in one coating run.




TASK: Improve Cr:ZnSe crystal’s performance with anti-reflection coatings

Chromium doped Zinc Selenide (Cr:ZnSe) is used as laser crystal in MWIR lasers. 3photon IR BBAR coating on Cr:ZnSe reduces light losses on both crystal ends.




Challenge us with your task for IR coatings!

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